Field of the invention: This invention is related to water soluble or water dispersible reaction products and their use as coating compositions.
Description of the prior art: The reaction of monomeric alkylene oxides with organic sulfides (i.e. thioethers) in the presence of various acids is well known. Such reactions are described, for example, in U.S. Pat. Nos. 3,159,682, 3,184,477, 3,538,132 and references cited therein. The reaction of an epoxy resin with an organic sulfide in the presence of an acid was more recently described by DeBona in U.S. Pat. No. 3,793,278.
In U.S. Pat. No. 3,793,278 epoxy resins of relatively low epoxy equivalent weight (EEW) were reacted in a substantially organic medium with certain organic sulfides in the presence of an acid having a dissociation constant greater than 1 .times. 10.sup..sup.-5 to thus form a "quaternary sulfonium salt group -- containing resin" which was subsequently dispersed in water. The patentee states that such aqueous dispersions are useful as coating compositions and are particularly useful as electrodepositable coating compositions which deposit upon a cathode. The patentee states that his reaction products can be characterized as "a water-containing medium containing an ungelled water-dispersible epoxy resin having at least one 1,2-epoxy group per average molecule, and chemically-bound quaternary sulfonium base salts". Such products are achieved as noted above by reacting low molecular weight epoxy resins (e.g. those having an EEW of up to about 300) with a sulfide in the presence of certain acids (specifically lactic acid). The reaction between such components occurred at temperatures of from 70.degree. to 110.degree. C, normally in an organic solvent. The ratio of reactants in the process was chosen by the patentee such that there was at least one equivalent of acid per equivalent of sulfide. The ratio of sulfide to epoxy group in the epoxy resin was said to be variable so long as the final resin contained an average of at least one epoxy group per molecule. These products are more fully described in a U.S. Pat. application Ser. No. 217,278 by Wismer and Bosso entitled "Epoxy Compositions" filed Jan. 12, 1972 (see German Pat. application No. 2,261,804, filed Dec. 16, 1972). The thermal curability of sulfonium compounds alluded to by the patentee in U.S. Pat. No. 3,793,278 is an important property which was demonstrated by Hatch in U.S. Pat. No. 3,544,499. Electrodeposition of water-soluble mono-sulfoniums was taught in U.S. Pat. No. 3,852,174 and the electrodeposition of water-soluble polysulfonium compounds was shown by U.S. Pat. No. 3,697,398.